1. Field of the Invention
The present invention relates to endoscope apparatuses for directly observing a body cavity or the lumen of an organ, and particularly to an endoscope apparatus for illuminating a tissue with excitation light to allow an affected site to be observed for diagnosis using fluorescence generated by the tissue.
2. Description of Related Art
Technologies for generating a fluorescence image by detecting autofluorescence from a tissue or fluorescence generated by a chemical agent administered to the tissue with an endoscope apparatus in order to examine biological tissues for degeneration or disease such as cancer based on this fluorescence image are known.
Endoscope apparatuses for performing fluoroscopy are described in, for example, Japanese Unexamined Patent Application Publication No. Hei-7-155285 and Japanese Unexamined Patent Application Publication No. Hei-10-243920.
The endoscope apparatus described in Japanese Unexamined Patent Application Publication No. Hei-7-155285 has a structure for selectively displaying a normal endoscopic image or a fluorescence image depending on the amount of light in the fluorescence image. With this structure, not only can the image be easily switched between an endoscopic image and a fluorescence image, but a lesion can be distinguished from normal tissue according to the amount of light in the fluorescence image for successful fluoroscopy of the lesion.
The endoscope apparatus described in Japanese Unexamined Patent Application Publication No. Hei-10-243920 has a structure for allowing a normal endoscopic image and a fluorescence image to be observed, as well as allowing the distance between an excitation-light irradiating section and a tissue to be measured and the output of an excitation light source to be adjusted according to the measured distance. With this structure, a fluorescence-detecting unit enables fluoroscopy with constant gain regardless of the distance between the excitation-light irradiating section and the tissue.